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package java.security.cert;

import java.io.InputStream;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.security.Provider;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the {@code CertificateFactory} class.
 * All the abstract methods in this class must be implemented by each
 * cryptographic service provider who wishes to supply the implementation
 * of a certificate factory for a particular certificate type, e.g., X.509.
 *
 * <p>Certificate factories are used to generate certificate, certification path
 * ({@code CertPath}) and certificate revocation list (CRL) objects from
 * their encodings.
 *
 * <p>A certificate factory for X.509 must return certificates that are an
 * instance of {@code java.security.cert.X509Certificate}, and CRLs
 * that are an instance of {@code java.security.cert.X509CRL}.
 *
 * @author Hemma Prafullchandra
 * @author Jan Luehe
 * @author Sean Mullan
 * @see CertificateFactory
 * @see Certificate
 * @see X509Certificate
 * @see CertPath
 * @see CRL
 * @see X509CRL
 * @since 1.2
 */

public abstract class CertificateFactorySpi {

  /**
   * Generates a certificate object and initializes it with
   * the data read from the input stream {@code inStream}.
   *
   * <p>In order to take advantage of the specialized certificate format
   * supported by this certificate factory,
   * the returned certificate object can be typecast to the corresponding
   * certificate class. For example, if this certificate
   * factory implements X.509 certificates, the returned certificate object
   * can be typecast to the {@code X509Certificate} class.
   *
   * <p>In the case of a certificate factory for X.509 certificates, the
   * certificate provided in {@code inStream} must be DER-encoded and
   * may be supplied in binary or printable (Base64) encoding. If the
   * certificate is provided in Base64 encoding, it must be bounded at
   * the beginning by -----BEGIN CERTIFICATE-----, and must be bounded at
   * the end by -----END CERTIFICATE-----.
   *
   * <p>Note that if the given input stream does not support
   * {@link java.io.InputStream#mark(int) mark} and
   * {@link java.io.InputStream#reset() reset}, this method will
   * consume the entire input stream. Otherwise, each call to this
   * method consumes one certificate and the read position of the input stream
   * is positioned to the next available byte after the inherent
   * end-of-certificate marker. If the data in the
   * input stream does not contain an inherent end-of-certificate marker (other
   * than EOF) and there is trailing data after the certificate is parsed, a
   * {@code CertificateException} is thrown.
   *
   * @param inStream an input stream with the certificate data.
   * @return a certificate object initialized with the data from the input stream.
   * @throws CertificateException on parsing errors.
   */
  public abstract Certificate engineGenerateCertificate(InputStream inStream)
      throws CertificateException;

  /**
   * Generates a {@code CertPath} object and initializes it with
   * the data read from the {@code InputStream} inStream. The data
   * is assumed to be in the default encoding.
   *
   * <p> This method was added to version 1.4 of the Java 2 Platform
   * Standard Edition. In order to maintain backwards compatibility with
   * existing service providers, this method cannot be {@code abstract}
   * and by default throws an {@code UnsupportedOperationException}.
   *
   * @param inStream an {@code InputStream} containing the data
   * @return a {@code CertPath} initialized with the data from the {@code InputStream}
   * @throws CertificateException if an exception occurs while decoding
   * @throws UnsupportedOperationException if the method is not supported
   * @since 1.4
   */
  public CertPath engineGenerateCertPath(InputStream inStream)
      throws CertificateException {
    throw new UnsupportedOperationException();
  }

  /**
   * Generates a {@code CertPath} object and initializes it with
   * the data read from the {@code InputStream} inStream. The data
   * is assumed to be in the specified encoding.
   *
   * <p> This method was added to version 1.4 of the Java 2 Platform
   * Standard Edition. In order to maintain backwards compatibility with
   * existing service providers, this method cannot be {@code abstract}
   * and by default throws an {@code UnsupportedOperationException}.
   *
   * @param inStream an {@code InputStream} containing the data
   * @param encoding the encoding used for the data
   * @return a {@code CertPath} initialized with the data from the {@code InputStream}
   * @throws CertificateException if an exception occurs while decoding or the encoding requested is
   * not supported
   * @throws UnsupportedOperationException if the method is not supported
   * @since 1.4
   */
  public CertPath engineGenerateCertPath(InputStream inStream,
      String encoding) throws CertificateException {
    throw new UnsupportedOperationException();
  }

  /**
   * Generates a {@code CertPath} object and initializes it with
   * a {@code List} of {@code Certificate}s.
   * <p>
   * The certificates supplied must be of a type supported by the
   * {@code CertificateFactory}. They will be copied out of the supplied
   * {@code List} object.
   *
   * <p> This method was added to version 1.4 of the Java 2 Platform
   * Standard Edition. In order to maintain backwards compatibility with
   * existing service providers, this method cannot be {@code abstract}
   * and by default throws an {@code UnsupportedOperationException}.
   *
   * @param certificates a {@code List} of {@code Certificate}s
   * @return a {@code CertPath} initialized with the supplied list of certificates
   * @throws CertificateException if an exception occurs
   * @throws UnsupportedOperationException if the method is not supported
   * @since 1.4
   */
  public CertPath
  engineGenerateCertPath(List<? extends Certificate> certificates)
      throws CertificateException {
    throw new UnsupportedOperationException();
  }

  /**
   * Returns an iteration of the {@code CertPath} encodings supported
   * by this certificate factory, with the default encoding first. See
   * the CertPath Encodings section in the <a href=
   * "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathEncodings">
   * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
   * for information about standard encoding names.
   * <p>
   * Attempts to modify the returned {@code Iterator} via its
   * {@code remove} method result in an
   * {@code UnsupportedOperationException}.
   *
   * <p> This method was added to version 1.4 of the Java 2 Platform
   * Standard Edition. In order to maintain backwards compatibility with
   * existing service providers, this method cannot be {@code abstract}
   * and by default throws an {@code UnsupportedOperationException}.
   *
   * @return an {@code Iterator} over the names of the supported {@code CertPath} encodings (as
   * {@code String}s)
   * @throws UnsupportedOperationException if the method is not supported
   * @since 1.4
   */
  public Iterator<String> engineGetCertPathEncodings() {
    throw new UnsupportedOperationException();
  }

  /**
   * Returns a (possibly empty) collection view of the certificates read
   * from the given input stream {@code inStream}.
   *
   * <p>In order to take advantage of the specialized certificate format
   * supported by this certificate factory, each element in
   * the returned collection view can be typecast to the corresponding
   * certificate class. For example, if this certificate
   * factory implements X.509 certificates, the elements in the returned
   * collection can be typecast to the {@code X509Certificate} class.
   *
   * <p>In the case of a certificate factory for X.509 certificates,
   * {@code inStream} may contain a single DER-encoded certificate
   * in the formats described for
   * {@link CertificateFactory#generateCertificate(java.io.InputStream)
   * generateCertificate}.
   * In addition, {@code inStream} may contain a PKCS#7 certificate
   * chain. This is a PKCS#7 <i>SignedData</i> object, with the only
   * significant field being <i>certificates</i>. In particular, the
   * signature and the contents are ignored. This format allows multiple
   * certificates to be downloaded at once. If no certificates are present,
   * an empty collection is returned.
   *
   * <p>Note that if the given input stream does not support
   * {@link java.io.InputStream#mark(int) mark} and
   * {@link java.io.InputStream#reset() reset}, this method will
   * consume the entire input stream.
   *
   * @param inStream the input stream with the certificates.
   * @return a (possibly empty) collection view of java.security.cert.Certificate objects
   * initialized with the data from the input stream.
   * @throws CertificateException on parsing errors.
   */
  public abstract Collection<? extends Certificate>
  engineGenerateCertificates(InputStream inStream)
      throws CertificateException;

  /**
   * Generates a certificate revocation list (CRL) object and initializes it
   * with the data read from the input stream {@code inStream}.
   *
   * <p>In order to take advantage of the specialized CRL format
   * supported by this certificate factory,
   * the returned CRL object can be typecast to the corresponding
   * CRL class. For example, if this certificate
   * factory implements X.509 CRLs, the returned CRL object
   * can be typecast to the {@code X509CRL} class.
   *
   * <p>Note that if the given input stream does not support
   * {@link java.io.InputStream#mark(int) mark} and
   * {@link java.io.InputStream#reset() reset}, this method will
   * consume the entire input stream. Otherwise, each call to this
   * method consumes one CRL and the read position of the input stream
   * is positioned to the next available byte after the inherent
   * end-of-CRL marker. If the data in the
   * input stream does not contain an inherent end-of-CRL marker (other
   * than EOF) and there is trailing data after the CRL is parsed, a
   * {@code CRLException} is thrown.
   *
   * @param inStream an input stream with the CRL data.
   * @return a CRL object initialized with the data from the input stream.
   * @throws CRLException on parsing errors.
   */
  public abstract CRL engineGenerateCRL(InputStream inStream)
      throws CRLException;

  /**
   * Returns a (possibly empty) collection view of the CRLs read
   * from the given input stream {@code inStream}.
   *
   * <p>In order to take advantage of the specialized CRL format
   * supported by this certificate factory, each element in
   * the returned collection view can be typecast to the corresponding
   * CRL class. For example, if this certificate
   * factory implements X.509 CRLs, the elements in the returned
   * collection can be typecast to the {@code X509CRL} class.
   *
   * <p>In the case of a certificate factory for X.509 CRLs,
   * {@code inStream} may contain a single DER-encoded CRL.
   * In addition, {@code inStream} may contain a PKCS#7 CRL
   * set. This is a PKCS#7 <i>SignedData</i> object, with the only
   * significant field being <i>crls</i>. In particular, the
   * signature and the contents are ignored. This format allows multiple
   * CRLs to be downloaded at once. If no CRLs are present,
   * an empty collection is returned.
   *
   * <p>Note that if the given input stream does not support
   * {@link java.io.InputStream#mark(int) mark} and
   * {@link java.io.InputStream#reset() reset}, this method will
   * consume the entire input stream.
   *
   * @param inStream the input stream with the CRLs.
   * @return a (possibly empty) collection view of java.security.cert.CRL objects initialized with
   * the data from the input stream.
   * @throws CRLException on parsing errors.
   */
  public abstract Collection<? extends CRL> engineGenerateCRLs
  (InputStream inStream) throws CRLException;
}
